NEETZoologyMolecular Basis of Inheritance
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): If a double-stranded DNA molecule contains 20% Cytosine, the mRNA transcribed from it will not necessarily contain 20% Guanine. Reason (R): During transcription, RNA polymerase follows the rule of complementary base pairing where Cytosine of the template strand pairs with Guanine in the mRNA. In th
Options
- ABoth (A) and (R) are true and (R) is the correct explanation of (A)
- BBoth (A) and (R) are true but (R) is not the correct explanation of (A)
- C(A) is true but (R) is false
- D(A) is false but (R) is true
Correct answer
B. Both (A) and (R) are true but (R) is not the correct explanation of (A)
Step-by-step solution
Assertion (A) is true. In a double-stranded DNA, if Cytosine is 20%, it represents the average of both strands. The template strand alone could have any percentage of Cytosine (e.g., 10%), while the coding strand has the rest (e.g., 30%). Since mRNA is transcribed only from the template strand, its Guanine content will match the Cytosine content of the template strand, which is not necessarily equal to the 20% average of the entire dsDNA. Reason (R) is true. RNA polymerase adds Guanine to the mRNA when it reads Cyt